Crane with boom-stabilizing hold-down



March 12, 1968 A, U L BEIER ET AL 3,372,814

CRANE WITH BOOM-STABILIZING HOLD-'DOWN Filed Nov. 4, 1966 2 Sheets-Sheet i ARTHUR J. MUHLBEIIER DONALD J. WUDTKE INVENTOR.

ATIORNEYS A. J. MUHLBEIER ET AL,

CRANE WITH BOOM-STABILIZING HOLD-DOWN March 12, 1968 Filed Nov. 4, 1966 2 Sheets$heet 2 o E a o .8. 0 N 3 AJ t. n- L a m 1:88 w i i mm 5. mm mm UHLBEIER M QI United States Patent Ofilice 3,372,814 Patented Mar. 12, 1968 3,372,814 CRANE WITH BOOM-STABILIZING HGLD-DOWN Arthur J. Muhlbeier, Sedro Woolley, and Donald J. Wudtke, Burlington, Wash, assignors to Skagit Corporation, Sedro Woolley, Wash, a corporation of Washington Filed Nov. 4, 1966, Ser. No. 592,182 10 Ciairns. (Cl. 21239) ABSTRAQT OF THE DISCLOSURE say in a high wind. Wind-created instability is of course most apt to occur when the boom has been raised to an angle of 45 or more. The problem of instability is one to which ship-carried cranes are especially prone. An overturning moment may occur from a ships roll where the ship is called upon to load or unload cargo in open water.

As heretofore known, booms have relied upon cranes with vertically swingable the weight of the boom to resist overturning forces, augmented at times by the weight of a suspended load. However, such augmentation obtains only if the crane is not level-luifing. The problem of instability is of moment to any crane having a vertically swingable boom but is of even greater concern with level-luffing cranes.

The present invention aims to overcome boom instability and in its simplest concept this is accomplished by employing a hold-down line in conjunction with the topping line, with the hld-d0wn line attached to the underside of the boom, and so interconnecting the two lines that as one line pays out the other line is hauled in.

More particular objects and advantages will appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

Description of drawings:

In the accompanying drawings:

FIGURE 1 is a fragmentary side elevational view illustrating a derrick crane constructed in accordance with a simple embodiment of the invention;

FIG. 2 is a schematic portrayal of the rigging thereof.

FIG. 3 is a fragmentary side elevational view illustrating a modified and preferred system for accomplishing the coinciding pay-out of one line and take-in of the other; and

FIG. 4 is a view diagramming the operative interconnection which is provided between the two lines in said FIG. 3 embodiment.

Description of invention:

It is believed that clarity in an understanding of the invention will be advanced by first describing the embodiment which I have illustrated in FIGS. 1 and 2 of the drawings. The boom for the crane is denoted by the numeral 10. Such boom is forked at its inner end and the fork arms 11 straddle a swing platform 13 and are pivoted by pins 12 thereto for vertical swing movement about a horizontal axis which desirably traverses the vertical axis about which the platform turns. Giving support to the platform is a king-post 14, and

rising from the king-post is a as its floor contains machinery for the operation of the crane, and surmounting the machinery house is an operators cab 17. Included in said machinery are spooling drums and 21 for light and heavy load lines 22 and 23, respectively,'a spooling drum 24 for a topping line 25, and a spooling drum 26 for a boom-stabilizer line 27. The two drums 24 and 26 either rotate as one about a common axis, or, as here illustrated, are so interlocked that the rotations of the two bear a constant relationship. The purpose will hereinafter appear but suffice it to here say that as the topping line is taken in and paid out the stabilizer line 27 pays out and takes in, respectively, at correlated linear speeds.

The boom stabilizer line 27 passes from the drum 26 over one and under the other of two sheaves 39 and 31, thence runs outwardly to take a bight around a sheave 32 carried upon the underside of the boom in a position removed a substantial distance from the booms root end, and from said sheave 32 returns to the platform where it is dead-ended, as at 33. Said sheave 31 is spaced well to the front of the booms pivot 12 in a position which desirably is offset a moderate distance below the horizontal plane in which said pivot lies. As a compensating expedient, the stabilizer line admits to a resistant stretch action and this may be accomplished either by having the dead-ended end 33 wound upon a springloaded reel or, as here illustrated, including a heavyduty extension spring 34 within the length of the line.

The topping line 25 is rigged to provide a doublepurchase block-and-tackle connection in running between the head end of the mast and the cross-arm of a yoke 35 having its side arms each pivoted to a respective one of two brackets 36 which are fixed to the boom at the approximate mid-length thereof. Said rigging includes a pair of sheaves, as 3738 and 3940', at each of the two ends of the differential fall, and has the standing part fixed to the mast, as at 41.

For the two lines 22 and 23 of the hoisting drums 20 and 21, respectively, the rigging is here illustrated as being in each instance of a level-lufling character. This is to say that with the drums 2t and 21 held stationary, a load suspended from either the loading hook 42 or the loading hook 43, as the case may be, occupies substantially the same level regardless of any change in the angularity of the boom. In the instance of the lightload hoist line 22, there is provided a pair of sheaves, as 44-45 and 4647, as each end of a differential fall. In the instance of the heavy-load hoist line 23, there is provided at the mast end of a differential fall a set of three sheaves 49-5tl-51 and at the boom end of said fall two sets of sheaves, as 52-53 and 5455, spaced apart longitudinally of the boom. The light load hoist line 22 has its two ends attached one to the drum 20 and the other to the hook 42 and, considered from the drum to the hook, takes bights successively about the sheaves 44, 46, 45 and 47. The heavy-load hoist line 23 has its two ends attached one to the drum 21 and the other to the mast 15 and at its approximate mid-length takes a hang-bight about a sheave 48 to which the loading hook 43 is attached. Considered between the drum and said hanging sheave, the line passes successively around the sheaves 49, 5'2, 50 and 54. Considered between the dead-ended end and said hanging sheave, the line passes successively around the sheaves S3, 51 and 55.

From the foregoing it will be apparent that any tendency for the boom to rise, by a force or forces other than lift exerted from the topping line, is countered by the stabilizer line in that the distance between. the localized sheave 31 and the boom-carried sheave 32 increases with a decrease in the distance between the boom-carried 3 sheaves 39-40 and the localized sheaves 37-68. he interlocked association between the drums 2d and z permits a run-out of the stabilizer line only in concert with a takein of the topping line.

In the other and preferred embodiment which I illustrate in FIGS. 3 and 4 there is substituted for the drum 26 a stabilizing control comprised of two sets of two sheaves sa en and til. 61 connected by the piston-andcylinder components of a single-acting hydraulic jack. Such control is or may be housed in a hollow center of the mast with the two sheaves some journaled upon a cross-shaft 64 for rotation about a fixed horizontal axis. The two sheaves 6l--ol lie below the sheaves and receive a rotary journal from a cross-shaft 65 guided from side walls of the mast for vertical movcmit in a prescribed path. The cylinder 66 of the hydraulic jack connects with one of the two cross-shafts while a rod 67 from the jack piston as connects with the other crossshaft. The inner end of the stabilizer line, here denoted by 76, passes from the sheave Sq; under a sheave '71 located at the base of the mast and thence runs upwardly to take a bignt about one of the two fixed sheaves 6%. Rights are then taken in turn about one of the movable sheaves, the other fixed sheave, and the other movable sheave, being then dead-ended to the cylinder of the jack.

The jack is contained in a hydraulic circuit (FIG. 4) which has a fluid reservoir 72, a variable volume pump '73 with an associated pressure compensator '74, said pump drawing fluid from the reservoir and supplying the same to a pipe 8t} which connects with the jack cylinder 66, a pressure-relief valve 77, and a control 76 occupying an intervening position between said pipe 8t} and the pressure-relief valve and which is made to respond to a device which senses changes in the tension co.dition of the topping line 25. The pressure-relief valve is set to a moderate level of, say, 250 psi. The two pipes, one leading from said pipe as to a front-side port of the control 76 and the other leading from a back-side port of the control to the pressure-relief valve 77, are denoted by S1 and 82, respectively. A valve 83 sprmg-biased into an open position provides a normal full-flow connection from the front-side port to the back-side port. A choked connection 86 by-passes the valve. The valve is either mechanically closed, say by a cam, or by an energizing of the indicated solenoid 87, in either case responding to a drop in the tension of the topping line below a predetermined level.

For purposes of illustration I have shown the tensionsensing device as comprising a sheave 9t? over which the topping line 25 passes. The topping line, when in a normal taut condition, acts against the yielding resistance of a spring st to swing the sheave into a position whcreat the same acts through a limit switch to open a relay electric circuit including the solenoid $7.

With said valve 83 open the pumped fluid flows tl'rrough the relief valve to the reservoir, albeit maintaining within the hydraulic system a pressure (250 psi.) sufficient to esp the stabilizing line from running slack. Should the topping line 25 become slack, evidencing an unstable condition of the boom, the electric circuit to the solenoid is closed and valve 83 responsively closes. Pressure instantly builds up in the line 8%} and the pump 73 supplies fluid at high pressure to the cylinder as of the jack, cans ing the jack piston to force the movable sheaves il-6l of the stabilizing control downwardly. This provides a take-up upon the stabilizer line 7b so that a downward force of considerable intensity is exerted upon the boom until there is reestablished upon the topping line a condition of tautness-evidencing restored boom stability sufficient to again open the circuit to the solenoid.

The pump '73 which we prefer to employ has the capacity of pumping from gpm. to 29 gpm. The pressure compensator 74 strokes the pump to zero delivery when the pressure in the hydraulic system reaches 3000 A. psi. At a pressure anywhere below 2909 psi. the compensator causes the pump to deliver 29 gpm.

Upon a closing of said valve S3reilecting an unstable condition of the boom-the pressure in the system goes to 3000 p.s.i., which will stabilize the boom. If the boom sits at this position, the pump 73 will be stroked towards zero delivery by the pressure compensator to the volume required to hold at 3060 p.s.i., i.e., it will deliver just the volume of oil required to make up for internal leakage in the system. This type of pump, controlled by a pressure compensator, does not build up heat in the system.

The stabilizing device will also pull the boom down while the same is in an unstable condition if a signal is given by the topping hoist master control to lower the boom.

It is thought that the invention will have been clearly understood from the foregoing detailed description of my now-preferred illustrated embodiments. Changes in the details of construction may be resorted to without departing from the spirit of the invention and it is accordingly my intention that no limitations be implied and that the hereto annexed claims be given the broadest interpretalion to which the employed language fairly admits.

What is claimed as new, is:

i. In a crane, a stand, a hoisting boom pivoted to the stand for vertical swing movement, a topping line for the boom, powered means under the control of an operator for paying out and taking in the topping line so that the boom will be responsively lower d and raised in the respective instance, and a means operatively interconnected with the boom for exerting thereon a stabilizing arrestation force when an influence other than the topping line subjects the boom to a lifting moment.

2. A- crane according to claim 1 in which said boomstabilizing means is made to perform its arresting function automatically in response to the imposition upon the boom of said other lift influence.

3. A crane according to claim 1, the stabilizing means being comprised of a running line included in rigging taking a purchase upon the underside of the boom at a point thereon removed a substantial distance from the booms pivotal axis and acting by a take-up on the line to subject the boom to a downward pull force.

4. A crane according to claim 3 in which as the line related to one drum is taken in or payed out the line related to the other drum is payed out and taken in, respectively, at linear speeds which are correlated in a predetermined ratio one said line to the other line.

5. A crane according to claim 3 in which the stabilizing line admits to a limited amount of resistant stretch.

6. A crane according to claim 1, the stabilizing means bein comprised of a running line included in rigging taking a purchase upon the underside of the boom at a point thereon removed a substantial distance from the booms pivotal axis and acting by a take-up on the line to subject the boom to a downward pull force, the run ning end of said stabilizing line being trained about the two sets of sheaves of a difierential pulley assembly carried upon the stand, the pulley assembly having an extensible powered spreader extending between the two sets of sheaves for taking up on the stabilizing line.

'7. A crane according to claim 6 in which the extensible spreader is comprised of the piston-and-cylinder components of a hydraulic jack.

8. A crane according to claim 6 in which a means is provided for sensing in the topping line a tension condition less than a given norm, and means made to operate automatically when said below-normal tension condition is sensed by the sensing means for causing said spreader to be extended and responsively take up on the stabilizing line.

i A crane according to clai .1 3 in which a means is provided for sensing in the topping line a tension condiliOn less than a given norm, and means operatively 5 5 interconnected with the stabilizing line and made to oper- References Cited ate antomatically when said below-normal tension condi- UNITED STATES PATENTS t10n 1s sensed by the sensing means for taking up on the stabilizing line until the tension condition of the topping 2,126,118 8/1938 Kelby 21239 line returns to said given norm. 5 2,393,312 1/1946 Davenport 212.39 It). A crane according to claim 1 characterized in that 23530310 4/1958 Banks the same is derrick yp and level-lufiing- ANDRES H. NIELSEN, Primary Examiner. 

